Loud speaker



Sept 2:5, 1934. B. A. ENGHOLM LOUD SPEAKER Filed Jan. 15 1935 PatentedSept. 25, 1934 I I. j LOUD SPEAKE Bernard -A. Engholm, Cleveland, 'Ohio,assignor' I to The Role Company, Cleveland, Ohiog a cor.-

poration of Ohio Application January 13, 1933, swarm. 651,549

3 Claims.

This invention relates to loud speakers, and particularly to devices forcentering the diaphragm and its associated voice coil in proper positionwith relation to the air gap between the inner and outer magnetic polepieces. A device for this purpose is commonly called a spider, and ispositioned either outside the voice coil or inside the diaphragm. In thefirst instance, it is called an outside spider, and in the second, aninside spider. The spider to be satisfactory must have sufficientrigidity to hold the diaphragm and associated voice coil in accurateposition, and at the same time, must have sufiicient flexibility topermit the necessary piston action of the coil and diaphragm.

A phenolic condensation product similar to bakelite may be used for thispurpose, for it can be pressed in sheet form and cut to the desiredshape. Due to its inherent characteristics however, it cannot besatisfactorily formed to provide a flange for anchoring it in place, ashas been the practice with a paper spider. The flange however, isobjectionable since it has a certain I amount of mass, which necessarilyresults in a lowered efficiency of the reproducer. Furthermore, sincethe flange is a solid annulus, it has objectionable circumferentialresonance. These considerations have limited the use of a phenoliccondensation product to outside spiders, where the material can becemented to the voice coil form, and secured at the marginal edges to asupport. I

An object of my invention therefore, is to provide a spider mounting,which can be used satisfactorily for an inside spider, and which willpermit the use of a material, such as a phenolic condensation productwithout requiring the utilization of a flange for attaching the spiderto a diaphragm. An additional object is to provide an arrangement,whereby the spider may be readily inserted into the assembly, andattached or locked in a convenient and inexpensive manner.

Referring now to the drawing, Fig. 1 is a side elevation, partly insection, of aloud speaker embodying my invention; Fig. 2 is a sectiontaken through the speaker diaphragm on the line 22 in Fig. 1; Fig. 3 isa section taken on the diaphragm with thespider removed; Fig. 4 is afront view of one of the spider sections illustrated in Fig. 2, whileFigs. 5, 6 and 7f are front views of modified forms of spiderconstruction.

I have shown my invention in connection with aloud speaker, which has adiaphragm 10, a voice coil 11, a diaphragm housing 12, a field coil 13and a field coil shell 14. The voice coil is disposed within an air gap,as for instance between an inner pole piece 15' and an outer pole piece16, while the diaphragm which is attached to the voice coil form issupported adjacent its outer end by the housing and adjacent its innerend by the spider indicated in general at 20. This is shown as an insidespider, which is fastened at its central portion to a projection 21 ofthe inner pole piece by a fastening member 22.

, 'Io permit the spider to be made of a phenolic condensation productand at the same time to facilitate its attachment to the diaphragm, Iprovide tabs 25 on the spider which project through spaced slots 26 inthe diaphragm and which can be cemented to the back of the diaphragm, asat 32. In the form shown, the spider comprises two similarly shapedsections, each of which is provided with a semi-circular recess as at 28which extends around the threaded shank of the fastening member 22. Thetwo recesses coact to provide a circular opening, which is larger thanthe diameter of the screw shank, so as to provide adequate clearance forany lateral adjustment that may have to be made to center the voice coilin the air gap.

In Fig. 5, the spider is shown as one piece unit but. in the preferredarrangement two pieces are used for this purpose. -This facilitates theassembly without requiring either the diaphragm to be distorted or thespider to be bent to insert the tabs during the assembly operation. Ineach case however, the spider preferably has radial portions 30, whichare connected by circular segmental portions 31. This arrangement maytake various forms, as is observable from an inspection of Fig. 6 andFig. '7 in comparison with Fig. 2. It is also apparent that the numberof radial portions and connecting circular segmental portions may bevaried in accordance with the size of the diaphragm with which thespider is to be used. In Fig. 2 for example, each section of the spiderhas an inner and outer and two" intermediate circular segmentalportions, while the spider of Fig. 6 has an inner and outer and oneintermediate circular segmental portion, and the spider of Fig. 7 hasinner and outer segmental portions only.

From the foregoing description, it will be apparent that this inventionprovides a spider construction which may be readily attached and whichpermits the use of a phenolic condensation product on an inside spiderassembly. While I have illustrated and described the shape of 'thespider as being preferably concerned with radially extending portionsthat are connected by circular extending segmental portions, it is to bereadily understood that such shapes may be varied without departing fromthe spirit of my invention.

I claim:-

1. In combination, a loud speaker diaphragm and an inside spiderassociated therewith, said spider comprising two similarly formedsections disposed in substantially the same plane and means on thespider for piercing a diaphragm and looking it thereto.

2. In combination, a loud speaker diaphragm, having a plurality ofopenings therein in substantially the same plane, a spider associatedwith the diaphragm and having tabs thereon that project through theopenings, and having a ing the Inidportion of the spider on the innerpole piece within the diaphragm, and said spider having tabs thatproject through the openings in the diaphragm, and make a tight fittherewith for locking the spider and diaphragm together as a unit.

BERNARD A. ENGHOLM.

